You should be able to achieve this all by changing two settings in the HikaShop backend.
a) Go to -> Display -> Content menus, and open the menu with ID 237. In the left pane, find "Number of columns" and change from "3" to "1". Save, then reload and check the frontend of your site - your product listing should be only a single column wide... possibly also wide enough to not break the product title line.
b) In the backend, go to -> System -> Configuration -> Main tab -> Images, and change the values for "Thumbnail width" (and "height") according to your preferences. Eventually also play with the settings for "Force images size" and/or "Image scale mode". Again, save and reload frontend.